AP BIOLOGY

THE CELL

CELL COMMUNICATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
How are steroid and protein hormones different?
A
steroid hormones are hydrophobic while protein hormones are hydrophilic
B
steroid hormones are hydrophilic while protein hormones are hydrophobic
C
steroid hormones are small and uncharged while protein hormones are large and charged
D
steroid hormones are large and charged while protein hormones are small and uncharged
Explanation: 

Detailed explanation-1: -3. Hormonal transport-some hormones can travel freely in the blood because they are water soluble (hydrophilic). The steroid hormones, being fat soluble (hydrophobic), must be bound to and carried around by transport proteins (like albumin and globulins which are blood proteins produced by the liver).

Detailed explanation-2: -Hydrophobic hormones are able to diffuse through the membrane and interact with an intracellular receptor. In contrast, hydrophilic hormones must interact with cell membrane receptors. These are typically associated with a G protein, which becomes activated when the hormone binds the receptor.

Detailed explanation-3: -Protein hormones react with receptors on the surface of the cell, and the sequence of events that results in hormone action is relatively rapid. Steroid hormones typically react with receptor sites inside a cell. Because this method of action actually involves synthesis of proteins, it is relatively slow.

Detailed explanation-4: -Although a few hormones circulate simply dissolved in the blood, most are carried in the blood bound to plasma proteins. For example, all the steroid hormones, being highly hydrophobic, are transported bound to plasma proteins.

Detailed explanation-5: -Lipophilic hormones or hydrophobic hormones are lipid-soluble hormones. These hormones can cross the phospholipid layer of the target cell membrane easily, as a result, it enters the target cells and binds to the intracellular receptors to perform their function. Some examples are steroid hormones and thyroid hormones.

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